Degreening
Product Care

Citrus fruit produced in Guyana is often mature and of acceptable eating quality when the rind is still green. However, many consumers in non-Caribbean export markets associate external skin color with internal flavor and believe oranges, tangerines, grapefruit, and lemons with green-colored peels are immature and not ready to eat. Demand in these markets is only for fully colored citrus fruits.

Purpose of Degreening

In order to improve external skin color and export market acceptance, citrus can be treated with ethylene, which is a naturally produced plant growth hormone effective as a de-greening agent. Ethylene treatment breaks down the green chlorophyll pigment in the exterior part of the peel and allows the yellow or orange carotenoid pigments to be expressed. This treatment is only cosmetic and does not alter the flavor of the fruit.

Timing of Degreening

De-greening treatment should be given immediately after harvest. Fruit do not have to be dry before treatment. Ethylene must be prior to waxing. Application of wax coating to the fruit surface will decrease the effects of the de-green process if applied first.

Ethylene Degreen Methods

There are several different methods of de-greening treatment:

• Gas Treatment
• High Pressure Cylinders
• Ethylene Generator
• Liquid treatment (Ethephon)

Only the liquid treatment (ethephon) is currently available in Guyana. The general procedure involves dipping green-skinned fruit in a tank of water at ambient temperature to low concentrations of ethylene for several minutes.

The source of ethylene is the chemical [(2-chloroethyl) phosphoric], which is liquid ethylene-releasing compound with the chemical name ethephon.

Water used should be sanitized using hypocholorous acid using 2.4 pints of household bleach per every 100 gallons of water, maintaining a pH of 6.5. The sanitizing strength of the wash water should be frequently tested and adjusted as necessary. A fungicide can also be incorporated into the water either benomyl or thiabendazole.

The following conditions should be reached when the liquid treatment is being carried out:

• Water Temperature (22-29°C) (72-85°F)
  Water Sanitation
  • Potable
  • 150 ppm hypochlorous acid
  • pH 6.5, fungicide benomyl (500 ppm)
    or thiabend azole (1000 ppm)
• Ethephon Concentration 500 ppm
• Duration: 1-3 minutes

Ethephon to water ratio: 10 ml Ethephon : 1 gallon water

Undesirable Effects of Degreening

Postharvest decay may be accelerated due to excess ethylene exposure. The two principal diseases which can increase are stem-end rot (Diplodia natalensis) and anthracnose (Colletotrichum gloeosporioides). Both pathogens can be controlled by a postharvest application of benomyl (500 ppm) or thiabendazole (1000 ppm) after de-greening.

Conclusion

The appearance of the produce is directly related to the consumer’s readiness to purchase the commodity. It is recommended that individuals interesting in exporting citrus to the European Markets, Canada, the USA and the Caribbean de-green citrus.

Liquid Ethelyene (Ethephon) is available at:

Caribbean Chemicals.
45 Croal St., Stabroek, Georgetown
Tel: 225-1478/225-9639
Fax: 225-8935
OR: C, Anna Regina, Essequibo
Tel: 771-5060

Cost: 100ml G$220.00; 250ml G$420.00

Disclaimer: Mention of companies or individuals on this website does not imply any endorsement by the Guyana Marketing Corporation.